The invention relates to an image pick-up module, in particular for an endoscope or a miniature camera, comprising an electronic image sensor having a plurality of contact fingers that are arranged in two rows on opposite sides, and a circuit board, to which the contact fingers are electrically contact-connected.
The invention furthermore relates to a method for assembly of an image pick-up module.
An electronic image pick-up module is generally used in video recording technology. Besides the use in video cameras, such electronic image pick-up modules are used, in as miniaturized a design as possible, in particular also in endoscopes for technical or medical purposes. Such an endoscope or video endoscope is disclosed for example in U.S. Pat. No. 5,754,313.
An image pick-up module generally comprises an electronic image sensor or image pick-up that converts light incident on it into an electrical signal. Generally, such electronic image sensors are embodied using CCD or CMOS technology.
Thus, miniaturized image sensors that are produced using TAB (tape automated bonding) technology are preferred at the present time. Image sensors of this type have contact fingers that are arranged in two rows on opposite sides of the image sensor and are contact-connected to the circuit board of the image pick-up module.
The circuit board of the image pick-up module serves not only for contact-connecting the image sensor, but also, as in the case of the image pick-up module disclosed in DE-A-199 24 189, for receiving electronic components, such as transistors or capacitors, which constitute parts of the control electronics of the image sensor.
In the case of the known image pick-up module just mentioned, the circuit board is formed from a one-part plate that can be folded along flexible connecting sections and can be folded to form a parallelepipedal body that is essentially U-shaped in cross section. In the folded state, the circuit board body has two sections that extend essentially transversely with respect to the image sensor and are spaced apart from one another and a third section running essentially parallel to the image sensor, the image sensor being fitted to that end of the first and second sections of the circuit board body which is at a distance from the third section. The third section of this circuit board of the known image pick-up module serves for the leadthrough of an electrical cable leading away from the circuit board, and in particular for the strain relief for this cable. By contrast, electronic components for the control electronics of the image sensor are fitted on the inner side of a fourth section of the circuit board, from the outer side of which the image sensor is arranged.
The use of such image pick-up modules in endoscopes has only become possible due to the miniaturization of the image sensors and the advances in microtechnology. In an endoscope, the image pick-up module is usually arranged in the distal tip, that is to say the tip facing the patient, of the endoscope shaft, as is described for example in U.S. Pat. No. 5,754,313. In this case, the image pick-up module replaces the image transmission optical system that is provided in “traditional” endoscopes and is formed from a serial arrangement of lenses. Instead of transmitting the image received at the distal end to the proximal end, that is to say to the end remote from the patient, by means of an optically imaging lens system, in an image pick-up module the optical light signals are converted into electrical signals and transmitted to the proximal end to the camera control unit via at least one cable or generally a cable system.
In endoscopes, the outer contour of the shaft is always required to have the smallest possible cross section. Accordingly, the image pick-up modules used have to have the smallest possible external cross section in order to find space in such a shaft. By way of example, in the case of a video endoscope for medical purposes, the shaft diameter is only a few mm, in any event less than 10 mm. This means that the dimensions of the miniaturized image pick-up module should be embodied as small as feasibly possible, i.e. as far as possible less than 6 mm. A compact design of an image pick-up module is therefore desirable.
On the other hand, the image pick-up module of integrated design should contain a series of components (e.g. amplifier) required for the function of the image sensor, so that the image pick-up module only also has to be connected to a customary multi-core cable which, in the case of using the image pick-up module in an endoscope in the distal tip thereof, produces the voltage supply and signal transmission between the image pick-up module and a control circuit (camera control unit) at the proximal end of the endoscope or in an external device.
The image pick-up module disclosed in U.S. Pat. No. 5,754,313 has two separate circuit boards, that is to say not a single circuit board in one piece for contact-connecting the image sensor, the two circuit boards, in a customary manner, receiving miniature electronic components and serving for contact-connecting the cable or cable system that leads away. In this case, the two circuit boards run parallel to one another and approximately at right-angles to the area of the image sensor. Since the signal electronics cannot function independently on the two circuit boards, an electrical connection, for example in the form of lines or a connecting circuit board, additionally has to be integrated, thereby increasing the mounting outlay of this known image pick-up module. The space between the two separate circuit boards is filled with a curing plastic. In this case, the cable moving away from the circuit board is contact-connected to the two circuit boards on the outer side thereof, and the contact fingers of the image sensor are likewise contact-connected to the circuit boards on the outer side of the two circuit boards at the distal end of the contact-making points of the cable leading away.
Consequently, this known image pick-up module also has a length in the transverse direction with respect to the image sensor which significantly exceeds the side dimensions of the image sensor.
A further requirement made of an image pick-up module of this type is that the image pick-up module should be able to be produced cost-effectively and with little time being spent; in particular, the assembly of the individual components of the image pick-up module should be able to be carried out as simply as possible despite the miniaturization and compactness of the image pick-up module.
U.S. Pat. No. 4,745,471 describes a further image pick-up module, in the case of which the image sensor is arranged on a one-piece circuit board that is U-shaped in cross section. In this case, the image sensor is embedded in the U-shaped groove of the circuit board, as a result of which, although a very short structural length in the direction transversely with respect to the image sensor is achieved, electronic components nevertheless then have to be fitted and contact-connected on the outer side of the circuit board in the case of this known image pick-up module, as a result of which these components have little protection against external influences.